Minimally Invasive Surgery for Decompression in Chiari I Malformation

Chiari malformations (CMs) includes different pathologies sharing common anatomic deformities of the brainstem and cerebellum. CM type I was originally introduced by Hans Chiari and described as an “elongation of the tonsils and the medial parts of the inferior lobes of the cerebellum into cone-shaped projections which accompany the medulla oblongata into the spinal canal.” The prevalence of CM has been estimated to be between 0.1% and 0.5%, but it is possible that higher rates will be identified since the increasing the use of magnetic resonance imaging (MRI) in common clinical practice. Clinical studies have shown an equal prevalence in both sexes without particular ethnic or geographic distribution. Also, there are no known risk factors other than family history for such pathology. By MRI findings, Aboulezz et al.2 established that in normal conditions, the tonsils tip can extend up to 3 mm below the foramen magnum, but a displacement of the cerebellar tonsils of at least 5 mm below the foramen magnum is commonly regarded as diagnostic for CM type I.